Ingotting machine

ABSTRACT

The invention concerns an ingotting machine comprising a certain number of double-walled ingot moulds cooled by water circulation and provided with means for the extraction of semisolid billets of metal, particularly steel. Preferably the ingot moulds are disposed rotatable around an axis and the machine comprises an indexing mechanism. In alternative the ingot moulds are disposed in a row and a container of melted metal moves from one to another to fill said moulds.

United States Patent 11 1 Brusa Oct. 16, 1973 [54] INGOTTING MACHINE3,501,125 3/1970 Fransson 164/131 X 1,350,352 8/1920 Anderson....164/325 [76] Invent: Ugo BN5, 30mm 1,698,308 1/1929 Lemcke 164/322 oodosso a, Italy 2,326,164 8/1943 Payne 164/136 x v 2,672,661 3/1954 Lutz164/326 [22] 1971 3,122,800 3/1964 Naffziger 164/326 x [21] Appl. No.:165,542

v Primary Examiner-J. Spencer Overholser 52 us. Cl. 164/325, 164/404Assistant Examiner-John Brown 51 Int. Cl 822d 5/02 Attorney-Clam Ceccon[58] Field of Search 164/131, 213, 322,

164/325, 326, 344, 348, 363, 126, 367, 136, 57 ABSTRACT The inventionconcerns an mgotting machine compris- [5 R f Cited ing a certain numberof double-walled ingot moulds UNITED STATES PATENTS cooled by watercirculation and provided with means for the extraction of semisolidbillets of metal, particufiP f larly steel, Preferably the ingot mouldsare disposed 2o8096l 5/1937 gg 49H. Ux rotatable around anaxis and themachine comprises 1:o73:988 9/1913 164,136 X an indexing mechanism. Inalternative the ingot 390,355 1011888 Fawcett 164/325 moulds aredisposed in a row and a container of 1317 1 3 93 Goad 164/131 X meltedmetal moves from one to another to fill said 1,936,280 11/1933 Williams249/174 UX moulds. 2,433,032 12/1947 Dempsey 164/344 X 2,893,081 7/1959Gerster 164/322 27 Claims, 22 Drawmg Figures 2,897,555 8/1959 Nishikiori164/136 X PATENTED [JET 16 I973 SHEET 9 BF 9 INGOTTING MACHINE Thepresent invention relates to an ingotting machine.

The object of the invention is to provide an ingotting machine forproducing billets of predetermined size.

The machine according to the invention is characterized in that iscomprises at least an ingot mould, whose size corresponds to the size ofthe billets to be produced, which is water cooled and has internal andexternal walls separated by a hollow space wherein the cooling watercirculates, at least said internal walls being made of a good heatconductor, for instance copper.

Another feature of the invention consists in that, at least in some ofits embodiments, the invention comprises means for extracting thesemisolid billet from the ingot mould.

According to a preferred embodiment the machine comprises a plurality ofingot moulds radially mounted around a rotating shaft and parallel tothe axis of said shaft, which is connected to a motor by which it isindexed so as to bring sequentially each ingot mould under a feedingdevice.

The axis of said shaft may be vertical or horizontal.

According to another embodiment the ingot moulds are aligned, and theirfeeding is obtained by carrying the feeder sequentially above eachmould. I

Advantageously the front portion of the ingot moulds may be hinged tothe rear portion and may be opened to allow the semisolid ingot to beextracted by means of a suitable device. v

According to a further embodiment the ingot moulds are arranged in twoor more rows,of which only one is so positioned as to be fed from thebottom through a suitable casting channel; when the feeding of one rowhas been finished, the adjacent row is presented at the feeding, by ahorizontal displacement, and 'so on; the rows previously fed through thechannel are brought to a position suitable for the extraction of thebillet.

According to a modified embodiment the mould rows are pivoted on ahorizontal axis and are moved to 1 a vertical casting position and thento a horizontal stripping position by means of a pivotal movement aboutsaid axis.

The invention will be better understood from the following description,with reference to the accompanying drawings, where:

FIG. 1 is a front elevational view ,ofapreferred embodiment of avertical axis ingotting machine according to the invention;

FIG. 2 is aplan viewof the same;

FIG. 3 is an axial section of the same;

FIG. 4 is a modification of FIG. 3 relating to the' feed- FIG. 5 is afront elevational view of a modification of this first embodiment;

FIG. 6 isa sectional view taken on a plane perpendicular to the axis ofthe ingotting machine of FIG. 5, and passing through one hinge;

FIG'. 7 is an axial section of this modified embodiment, showing also afirst embodiment of the devices for extracting the billets;

FIG. 8 is an elevational view, partly in section, of an ingottingmachine similar to the preceding ones, but provided with differentdevices for openingthe ingot moulds and extracting the billets;

FIG. 9 is a view from above and partly in section of the ingottingmachine of FIG. 8;

FIG. 10 is a vertical section of a machine according to the invention,with horizontal axis, and with a creeping feeding spout;

FIG. 11 is an elevational view, partly in section, of the same machine,showing also a device for extracting the billets;

FIG. 12 is a section in profile of the same;

FIG. 13 is a perspective view of another embodiment of the invention. I

FIG. 14 is a perspective view of a detail of the ingotting machine ofFIG. 13, showing the ingot moulds opened and theingots alreadyextracted;

FIG. 15 is a plan view of an ingot mould of this second embodiment;

FIG. 16 is a sectional view showing an ingot mould and the appertainingextracting device;

FIG. 17'is a modified embodiment of the preceding machine;

FIG. 18 is a perspective view of a third embodiment of the invention;

FIG. 19 is a vertical section of a part of the ingotting machine of FIG.18;

FIG. 20 is a vertical section of three rows of ingot moulds, accordingto. a modified embodiment of the above mentioned machine;

FIG. 21 is a longitudinal vertical section of the machine of FIGS. 18and 20, modified .in respect to the feeding;

FIG. 22 is a vertical section of an ingot mould taken in correspondenceof the channel connecting the ingot moulds. i

As shown in the drawing (FIG. 1), the ingotting machine according to a.preferred embodimentcomprises a number of ingot moulds 1 radiallymounted around a vertical shaft 2 and parallel to the axis of saidshaft.

The ingot moulds 1 are supported by aplate 3, solidary to the shaft 2,in which there are bottom shutters 4 (FIG. 3) which can be opened toallow the already formed billets 11 to be extracted. A .plate 5 similarto the plate 3 is .placed on the top of the ingot moulds 1 and isprovided, in correspondence'of each mould, with -openings ,6 (FIG. 2)which allow to pour into it the melted metal supplied'bya feeding device8.

'Said'feeding device may be spacedfrom the 'inlet openingsof the ingotmoulds l, or may creep on the plate 5 (FIG. 4): in this second case the:filled ingot mould is maintained under a certain pressure 'by theweight of the melted metal.

Theingot moulds'(FIG. 3) have internal and external walls 9, 9'separated'by a-hollow space .10 where water is circulated in order tomake the ingot .cooling easier;

at leastthe internal walls are advantageously made. of a good heatconductor, for instance copper.

The shaft 2 is provided with pulleys 12, 13, which allow connection to amotor.

According to a modification of this first embodiment each ingot mould isdivided in its longitudinal direction into two portions, for instancealong a plane passing through the middle points of two opposite sides:the front portion 1 of each ingot mould is hinged to the rear portion 1"by hinges 14 allowing the opening thereof (FIGS. 5 and 6).

The ingotting machines realized according to the described modificationare provided with meansfor extracting the billets and for sending themtowards subsequent working stations. Said means (FIG. 7) consists of anarm pivoted upon a pin 16 at its end nearer to. the ingotting machine;gripping members 17 allow to grip and to hold the ingot 11 which canslide on rollers 18 towards a conveyor, for instance a roller conveyor,a roller 19 of which is shown in FIG. 7.

According to a further modification, the ingot moulds are divided intheir longitudinal direction into two halves 1a, lb, for instance alongtwo opposite edges: the portion la is solidary to the machine, whereasthe portion lb is movable and is kept against the fixed half by means ofparallel pairs of hooks 22 pivoted on the walls of the fixed portion andpushed against the movable portion by a spring 23. Parallel tubes 24,placed along the walls alternately to the A pinion 20 meshing with awheel 21 indexes the ingotting machine. The bottom shutter 27 of eachingot mould may be opened and is pushed against the mould bottom by aset of rollers 28 placed along a certain are under the base of the ingotmoulds: the set of rollers 28 ends in correspondence witn an ingotextracting position. A device 29, operated by a jack 30 and apt to winthe force exerted by spring 23, is located in front of the machine insaid extracting position in order to open the hooks and to grip theexternal wall of the ingot mould. The ingot then goes out by gravitythrough the shutter 27 which is provided with a counterweight 31 whichcloses said shutter as soon as the ingot has passed through it. A chute32, ending in a portion 33 which bent to form an acute angle with theremaining portion of the chute, guides the falling ingot, the portion 33being so shaped as to assure that the billet upsets horizontally uponthe rollers 19 of a suitable conveyor.

A machine, similar to the one shown in FIGS. 1 to 7, but with horizontalaxis, is shown in FIGS. 10, 11, 12.

In such an embodiment shaft 2 is mounted on the uprights 34 by means ofthe bearings 35 allowing its rotation. The feeding of the .moulds ismade through a creeping spout 7 consisting of a reservoir 7a and acranked tube 7b whose end portion surrounds the inlet opening of theingot moulds and is always pressed against it by the weight of themolten metal.

The invention provides a device for extracting the semisolid ingots alsoin this embodiment: said device comprises a stem 36 ending in a head 3.7of greater diameter, and means, not shown, for bringing said head intocontact with the billets and for pushing them through the ingot moulduntil they arrive upon the rollers 19 of the conveyor.

According to another embodiment (FIG. 13) the ingot moulds I are alignedinstead of being mounted around a rotating shaft. The inlet openings arerealized in a rectangular plate 39; alsoaccording to this embodiment thefront portion 1' of each ingot mould is hinged to the rear portion bymean of hinges 14. The moulds are preferably arranged in groups of two,side by side, the hinges being mounted on the non-adjacent side walls,so that the front walls open in opposite directions; however said hingesmay be arranged so as to allow all the ingot moulds to open in the samedirection (FIG. 14).

The internal structure of the ingot moulds (see FIG. 15) is identicalwith that of the moulds of the previous embodiments.

The billets may be extracted and passed to the conveyor either directly(FIG. 14) or by means of the swinging arm of FIG. 16, similar to thatshown in FIG.

According to the modified embodiment shown in FIG. 17, the ingot mouldsare hinged at their base by means of a pivot 40, and, after having beenopened, may turn to the horizontal position so as to lay down directlythe billet 11 upon the rollers 19.

According to a further embodiment (FIGS. 18 and foll.) the ingot mouldsare arranged in two or more rows 41a, 41b only one of which, forinstance 41a, is at a given instant in such a position as to be fed,while the previously filled rows are then moved to a dischargingposition.

In the exemplary embodiment shown in FIGS. 18 and 19 the ingot mouldsare arranged in two rows and are mounted on a concave cylindrical base42 provided with wheels 43. The two rows can rotate around a fixedhorizontal axis realized by the two pins 44 at which the two rows arepivoted by means of the arms 46 of a plate 45 which surrounds threesides of the upper part of each row. A vertical container 49, slightlyhigher than the ingot moulds and formed by two frustums of cone ofrefractory material joined by their smaller bases, and a channel 47,realized in the base 42, allow the bottom feeding of the ingot moulds.

According to amodified embodiment (FIG. 20) the ingot moulds are mountedon a plane base, and the rows are presented .at the feeding ordischarging position with a horizontal movement of the rows themselves.

Finally, in the modified embodiment of FIGS. 21 and 22, the first ingotmould of each row is top fed, and the others are bottom fed through thechannel 48 provided in the bottom portion of the ingot moulds of eachrow.

The three ingot moulds shown in FIG. 20 relate each to one of saidfeeding methods.

The operation of the ingotting machine according to the invention is asfollows:

in order to fill the ingot moulds, the ladle with the melted steel ispositioned in such a way that the discharge opening is aligned with thetop opening of one ingot mould (FIGS. 3, 7, 8). When this ingot mouldhas been filled, the shaft 2 is rotated by a fraction of a revolution sothat the following ingot mould is brought into position; when this toohas been filled, a further rotation of the shaft will bring intoposition another ingot mould, and soon.

The number of the ingot moulds in each ingotting machine is determinedaccording to the cooling speed,

, so that, when the last ingot mould is filled, the billet formed in thefirst one is already cooled to such an extent that it can be extracted,so that an ingot mould is ready to be refilled at the subsequent step ofthe shaft.

In the embodiment shown in FIGS. 1 to 4 the ingot is extracted bygravity through the openable ingot mould bottom.

In the modified embodiment shown in FIGS. 5 to 7 the feeding of theingot moulds is made in the above described way. The ingot mould isopened by rotating the are so shaped and arranged that, when the arm isin the described position, they can grip the ingot near its ends. Thearm is then withdrawn to the horizontal position together with the ingotwhich is sent towards a conveyor by means of the rollers 18.

In the modified embodiment of FIG. 8 the ingot moulds are fed as abovedescribed. When the machine is rotating, the ingot mould bottom issupported by the rollers 28 along an arc corresponding to the path ofeach ingot mould from the feeding position to the ingot extractingposition. In the latter position the device 29 is brought into contactwith the external wall of the ingot mould, and removes the hooks 22 bymeans of the jack 30 by pushing in opposite directions the cylinders 22awith which the hooks are provided: in such conditions the device 29grips the portion lb of the ingot mould and moves it away from theportion 1a, and the billet, no longer held by the pressure of the Walls,opens the bottom shutter 27 by gravity and falls down along the chute 32as far as its bottom reaches the portion 33, which upsets the billetupon the rollers 19. As soon as the billet passes by, the counterweight31 closes again the shutter 27, the device 29 brings the portion lb ofthe ingot moulds again into contact with the portion la, so that thespring 23 thrusts again the hooks against the movable portion, afterwhich said device is moved away from the ingot mould and the machine maybe indexed again in order to go on with the filling and discharging ofthe ingot moulds.

In the embodiment with horizontal axis the feeding is made by a creepingspout: in order to fill the first ingot mould the spout is brought intocontact with the ingot mould head: when this mould has been filled, thepressures of the melted metal in the ingot mould and in the feedercoincide, so that the casting is automatically discontinued. During therotation of the machine the weight of the melted metal keeps thecreeping spout always in contact with the front portion of the ingottingmachine. For discharging the moulds, the rear shutter 38b of each ingotmould is opened and the stem 36 is introduced through the front shutterso that the head 37 is in contact with the base of the billet. A forwardmovement in the direction of the arrow X is given to said stem bysuitable means so as to bring the billet on the rollers 19; when thebillet has gone out, the stem 36 is drawn back and the ingot mould isready to be filled again.

In the embodiment shown in FIGS. 13 to 17, the ingot moulds are mountedon a fixed bearing, and then the feeding is made by moving the basketcontaining the metal over each ingot mould; the billet is extractedeither by means of the swimming arm described in a previous embodiment,or, in the case of the ingot moulds shown in FIG. 17, by pivoting theopen ingot mould around the pivot 40 so as to lay down the billetdirectly on the conveyor.

In the described embodiments that use vertical ingot moulds, the inletopenings may be advantageously realized so as to allow direct topfeeding by means of a ladle 8 (see FIG. 3). Alternatively the feeding ismade by a basket 8' (FIGS. 4, 7, 8) pressed against the mould head: alsoin this case, when the ingot mould has been filled, the melted steeltherein has the same pressure as the metal in the basket, so that thecasting is automatically stopped.

In the embodiment of FIGS. 18 and foll. the melted metal is introducedinto the first row of ingot moulds by bottom casting, or by top feedingthe first ingot mould of each row, from which the melted metal flows bybottom casting into the other ingot moulds. When the first row of ingotmoulds has been filled (FIG. 18), it is rotated around the axis 44 44,and the second row is brought into the vertical casting position bymeans of a similar rotation, and so on for the other rows. During therotation, the billets in the first ingot mould row cool to such anextent as to be extracted when the ingot mould row is in horizontalposition.

In the embodiment of FIG. 20 the filling is realized as described above;the ingot mould rows are brought sequentially into casting position bymeans of horizontal displacements, whereas the rows already fed arebrought into a position suitable for extracting the billet, still bymeans of horizontal movements: the billet is then extracted in one ofthe described ways.

I claim:

1. An ingotting machine characterized in that it comprises a rotatableshaft, a plurality of ingot moulds that are adapted to be water cooledand which have external and internal walls that are separated by ahollow space wherein the cooling water is adapted to be circulated, atleast said internal wall of each said mould being made of a heatconducting material, said ingot moulds being angularly spaced apart andpositioned radially outward of said shaft and means for extracting thesemi-solid ingot from the ingot mould, each said ingot mould having amovable front portion and a rear portion rigidly secured to the machine,said front and rear portions having the same length as the whole ingotmoulds, means for holding the movable portion against the fixed portionand means for urging said holding means against said movable portion.

2. An ingotting machine according to claim 1, characterized in that saidconductor is copper.

3. A machine according to claim 1 wherein said holding means comprisesparallel pairs of hooks hingedly mounted on said fixed portion and saidurging means comprises a spring.

4. An ingotting machine according to claim 1, characterized in that itcomprises means for indexing said shaft, so as to present sequentiallyall ingot moulds to a feeder of melted metal.

5. An ingotting machine according to claim 1 characterized in that theaxis of the shaft is vertical.

6. An ingotting machine according to claim 1 characterized in that theaxis of the shaft is horizontal.

7. An ingotting machine according to claim 1 characterized in that theingot mould bottom can be opened to allow the billet to be extracted.

8. A machine according to claim 1 characterized in that it comprises aplurality of aligned ingot moulds.

9. An ingotting machine according to claim 1, characterized in that aset of rollers is placed under the bottom of the ingot moulds and incontact with it along a certain arc, said rollers keeping said bottomclosed during the step-by-step movement that the machine performs tobring each ingot mould from the feeding position to the ingotdischarging position.

10. A machine according to claim 1 characterized in that the ingot mouldbottom is provided with a counterweight with which said bottomautomatically closes as soon as the billet goes out.

11. A machine according to claim 1 characterized in that it is providedwith jacks for separating the front and rear portions of the ingotmoulds when these portions are in said extracting position, and withmeans for guiding the falling ingot and for upsetting it in horizontalposition upon a suitable conveyor.

12. A machine according to claim 1 characterized in that the coolingwater is .led to the ingot moulds by a set of parallel tubes placedaroundtheir walls alternate to the hook pairs, said tubes acting also asa guide for a sliding movement of the movable portion of each ingotmould.

13. A machine according to claim 1 characterized in that each ingotmould has front and rear portions of the same length as the whole ingotmould, the front portion being hinged on the rear portion and beingopenable to allow the extraction of the billet.

14.A machine according to claim 13, characterized in that said ingotmoulds are hinged at their base and can be upset in order to lay downthe ingots on a suitable conveyor.

15. An ingotting machine according to claim 1, characterized in that themeans for extracting the semisolid billets comprises an arm which canrotate as far as to be parallel to the ingot moulds, said arm beingprovided with gripping means for gripping the ingot and with rollers forsending the ingot towards a conveyor.

16. An ingotting machine according to claim 1 characterized in that itis top fed.

17. An ingotting machine according to claim 1 characterized in that thefeeding of the ingot moulds is made by means of a basket or thundish 18.An ingotting machine according to claim 6, characterized in that it isfed by means ofa creeping spout.

19. A machine according to claim 6, characterized in that the means forextracting the semisolid ingot comprises a stem ending in an enlargedhead and means apt that it comprises two or more adjacent rows of ingotmoulds, only one of which is at a given instant at a feeding position,means for sequentially presenting all rows at the feeding, and means forbringing the rows already fed into a position apt to allow the ingotextraction.

21. An ingotting machine according to claim 20, characterized in thatthe ingot moulds are moved horizontally.

22. A machine according to claim 20, characterized in that theingotmoulds are pivotally connected to a horizontal axis, and are movedto a vertical casting position and then to a horizontal strippingposition by means of a rotation around said axis.

23. A machine according to claim 20 characterized in that the feeding ismade by bottom casting.

24. A machine according to claim 20 characterized in that the firstingot mould of each row is top fed, whereas the others are bottom fedthrough a channel provided in the bottom portion of each row of ingotmoulds.

25. A machine according to claim 19 characterized in that the ingotmould rows are mounted on a base provided with wheels.

26. A machine according to claim 25 characterized in that said base isplane.

27. A machine according to claim 25 characterized in that the uppersurface of said base has a cylindrical concavity.

1. An ingotting machine characterized in that it comprises a rotatableshaft, a plurality of ingot moulds that are adapted to be water cooledand which have external and internal walls that are separated by ahollow space wherein the cooling water is adapted to be circulated, atleast said internal wall of each said mould being made of a heatconducting material, said ingot moulds being angularly spaced apart andpositioned radially outward of said shaft and means for extracting thesemi-solid ingot from the ingot mould, each said ingot mould having amovable front portion and a rear portion rigidly secured to the machine,said front and rear portions having the same length as the whole ingotmoulds, means for holding the movable portion against the fixed portionand means for urging said holding means against said movable portion. 2.An ingotting machine according to claim 1, characterized in that saidconductor is copper.
 3. A machine according to claim 1, wherein saidholding means comprises parallel pairs of hooks hingedly mounted on saidfixed portion and said urging means comprises a spring.
 4. An ingottingmachine according to claim 1, characterized in that it comprises meansfor indexing said shaft, so as to present sequentially all ingot mouldsto a feeder of melted metal.
 5. An ingotting machine according to claim1, characterized in that the axis of the shaft is vertical.
 6. Aningotting machine according to claim 1, characterized in that the axisof the shaft is horizontal.
 7. An ingotting machine according to claim1, characterized in that the ingot mould bottom can be opened to allowthe billet to be extracted.
 8. A machine according to claim 1,characterized in that it comprises a plurality of aligned ingot moulds.9. An ingotting machine according to claim 1, characterized in that aset of rollers is placed under the bottom of the ingot moulds and incontact with it along a certain arc, said rollers keeping said bottomclosed during the step-by-step movement that the machine performs tobring each ingot mould from the feeding position to the ingotdischarging position.
 10. A machine according to claim 1, characterizedin that the ingot mould bottom is provided with a counterweight withwhich said bottom automatically closes as soon as the billet goes out.11. A machine according to claim 1, characterized in that it is providedwith jacks for separating the front and rear portions of the ingotmoulds when these portions are in said extracting position, and withmeans for guiding the falling ingot and for upsetting it in horizontalposition upon a suitable conveyor.
 12. A machine according to claim 1,characterized in that the cooling water is led to the ingot moulds by aset of parallel tubes placed around their walls alternate to the hookpairs, said tubes acting also as a guide for a sliding movement of themovable portion of each ingot mould.
 13. A machine according to claim 1,characterized in that each ingot mould has front and rear portions ofthe same length as the whole ingot mould, the front portion being hingedon the rear portion and being openable to allow the extraction of thebillet.
 14. A machine according to claim 13, characterized in that saidingot moulds are hinged at their base and can be upset in order to laydown the ingots on a suitable conveyor.
 15. An ingotting machineaccording to claim 1, characterized in that the means for extracting thesemisolid billets comprises an arm which can rotate as far as to beparallel to the ingot moulds, said arm being provided with grippingmeans for gripping the ingot and with rollers for sending the ingottowards a conveyor.
 16. An ingotting machine according to claim 1,characterized in that it is top fed.
 17. An ingotting machine accordingto claim 1, characterized in that the feeding of the ingot moulds ismade by means of a basket or thundish.
 18. An ingotting machineaccording to claim 6, characterized in that it is fed by means of acreeping spout.
 19. A machine according to claim 6, characterized inthat the means for extracting the semisolid ingot comprises a stemending in an enlarged head and means apt to introduce said stem intoeach ingot mould so that the head is in contact with the billet and aptto impart to said stem a forward movement within the ingot mould so asto thrust out the ingot.
 20. A machine according to claim 1,characterized in that it comprises two or more adjacent rows of ingotmoulds, only one of which is at a given instant at a feeding position,means for sequentially presenting all rows at the feeding, and means forbringing the rows already fed into a position apt to allow the ingotextraction.
 21. An ingotting machine according to claim 20,characterized in that the ingot moulds are moved horizontally.
 22. Amachine according to claim 20, characterized in that the ingot mouldsare pivotally connected to a horizontal axis, and are moved to avertical casting position and then to a horizontal stripping position bymeAns of a rotation around said axis.
 23. A machine according to claim20, characterized in that the feeding is made by bottom casting.
 24. Amachine according to claim 20, characterized in that the first ingotmould of each row is top fed, whereas the others are bottom fed througha channel provided in the bottom portion of each row of ingot moulds.25. A machine according to claim 19, characterized in that the ingotmould rows are mounted on a base provided with wheels.
 26. A machineaccording to claim 25, characterized in that said base is plane.
 27. Amachine according to claim 25, characterized in that the upper surfaceof said base has a cylindrical concavity.